1. Field of the Invention
This invention relates to a BGA (Ball Grid Array) type semiconductor device which has a plurality of ball-shaped conductive terminals and its manufacturing method.
2. Description of the Related Art
A CSP (Chip Size Package) has received attention in recent years as a three-dimensional mounting technology as well as a new packaging technology. The CSP means a small package having about the same outside dimensions as those of a semiconductor die packaged in it.
A BGA type semiconductor device has been known as a kind of CSP. A plurality of ball-shaped conductive terminals made of metal such as solder is arrayed in a grid pattern on one principal surface of a package of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.
When the BGA type semiconductor device is mounted on electronic equipment, the semiconductor die is electrically connected with an external circuit on a printed circuit board by compression bonding of the conductive terminals to wiring patterns on the printed circuit board.
Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in reducing size over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device is used as an image sensor chip for a digital camera incorporated into a mobile telephone, for example.
FIGS. 28A and 28B show outline structure of a conventional BGA type semiconductor device. FIG. 28A is an oblique perspective figure showing a top side of the BGA type semiconductor device. And FIG. 28B is an oblique perspective figure showing a back side of the BGA type semiconductor device.
A semiconductor die 104 is sealed between a first glass substrate 102 and a second glass substrate 103 through epoxy resin layers 105a and 105b in the BGA type semiconductor device 101. A plurality of conductive terminals 106 is arrayed in a grid pattern on a principal surface of the second glass substrate 103, that is, on a back surface of the BGA type semiconductor device 101. The conductive terminals 106 are connected to the semiconductor die 104 through a plurality of second wirings 110. The plurality of second wirings 110 is connected with aluminum first wirings 107 pulled out from inside of the semiconductor die 104, making each of the conductive terminals 106 electrically connected with the semiconductor die 104.
More detailed explanation on a cross-sectional structure of the BGA type semiconductor device 101 will be given hereafter referring to FIG. 29. FIG. 29 shows a cross-sectional view of the BGA type semiconductor devices 101 divided along dicing lines into individual dice.
The first wiring 107 is provided on an insulation film 108 on a top surface of the semiconductor die 104. The semiconductor die 104 is bonded to the first glass substrate 102 with the resin layer 105a. A back surface of the semiconductor die 104 is bonded to the second glass substrate 103 with the resin layer 105b. 
One end of the first wiring 107 is connected to the second wiring 110. The second wiring 110 extends from the end of the first wiring 107 onto a surface of the second glass substrate 103. And the ball-shaped conductive terminal 106 is formed on the second wiring 110 extended onto the second glass substrate 103.
However, there is a possibility that the first wiring 107 and the second wiring 110 are disconnected at a point of contact between them, since the area of the point of contact is very small in the BGA type semiconductor device 101 described above. Also there is a problem in step coverage of the second wiring 110.